Set the JBOSSAS_PIDFILE to JVM process pid

The JBossAS standalone.sh script use the 'JBOSS_PIDFILE' environment variable to store the PID of the JVM process. However in our control script we set the JBOSSAS_PIDFILE to the standalone.sh script PID, instead of the JVM pid. 

See:
https://github.com/openshift/origin-server/blob/master/cartridges/openshift-origin-cartridge-jbossas/versions/7/bin/standalone.sh#L208